Mobile phone networks have been initially conceived for allowing speech communication, similarly as with Public Switched Telephone Network (PSTN) but between mobile users. Mobile phone networks have experienced, and they are presently experiencing, a huge expansion, particularly subsequent to the introduction of the second-generation mobile networks, and notably digital mobile networks, such as those complying with the Global System for Mobile Communication (GSM) standard, and the corresponding systems adopted in the US, and in Japan.
Similarly to PSTN, the second-generation mobile networks are circuit switching networks; this greatly restrains the bandwidth which can be allocated for a certain user, particularly with second-generation mobile networks. In contrast, the data communication networks such as computer networks and, among these, the Internet, adopt packet switching schemes that allow much greater data transfer speeds.
A number of solutions have been proposed for overcoming the restraints of the traditional circuit switching mobile networks such as GSM networks, such as to allow the mobile terminal users to utilize the services offered by the Internet in an effective manner. One of the solutions that are becoming quite popular is the General Packet Radio Service (GPRS). GPRS is a mobile digital technology compatible with GSM networks (actually, it is constructed on the existing GSM network architecture) which allows higher speed data transfer than with pure GSM. Essentially, GPRS can be seen as an addition to GSM, which supports and makes feasible packet data communication. While third-generation wireless communication systems such as those complying with the Universal Mobile Telecommunication System (UMTS) standard are more promising in terms of data transfer speed, GPRS is nevertheless a solution at hand for improving the data exchange capacity in existing GSM networks.
The services offered by these mobile networks in addition to simple speech communications have quickly increased in quality and number; just to quote some examples, Short Messaging Systems (SMS) and Multimedia Messaging Systems (MMS), as well as Internet connection services have been recently provided.
Particularly, there is much interest in providing the mobile network users with multimedia services, i.e. services by which images, videos, data access through the Internet or e-mail can be added to a speech communication between users. Among these services, the so-called “combinational services” are attracting many mobile providers.
By “combinational service” herein is generally meant a service through which a terminal in a communication network (not necessarily a mobile one) can participate in two or more connections at the same time, which may be also based on different domains.
U. Olsson and M. Nilsson, in the article entitled “Combinational services—The pragmatic first step toward all-IP”, Ericsson Review No. 2, 2003, describe, inter alia, an example of the so-called “combinational services” in which the possibility is exploited of managing traffic in both circuit connection and packet connection at the same time: image sharing during a conversation between two users. The authors note that traffic can be simultaneously managed in a circuit connection and packet connection both with Wideband Code Division Multiple Access (WCDMA), which allows using multiple and parallel bearers in the “over-the-air” interface (multiple radio access bearers, multi-RAB) and with GSM, in which similar possibilities are offered by a standardized mechanism—the dual transfer mode, DTM.
Another description of a service that can be utilized by means of mobile terminals, similar to that discussed above, is given in White Paper “Video sharing—Enrich your voice call with video”, by Nokia Corporation, which is available for download at
http://www.nokia.com/BaseProject/Sites/NOKIA_MAIN_18022/CDA/Categories/Phones/Technologies/VideoSharing/_Content/_Static_Files/video_sharing_a4_2510.pdfThe real-time video sharing service allows two users to easily enrich their communication during a telephone conversation. Either of the users can share a live video recorded by a video camera, or video clips on his/her terminal. Both users watch the same video and can discuss the latter while continuing their voice call.
EP-A-847178 describes a multimedia conference service that employs parallel networks. This service offers the possibility of carrying out a voice conference by means of a PSTN network, and a data conference by means of a Internet or Web network. The network described in this document provides a conference management server administered by the PSTN network, which is able of controlling services offered by the PSTN network in response to signals from the external network, such as the Web network. The conference management server may be either administered by the PSTN network or simply it may be able of interworking with the PSTN network. In relation with image data, the conference management server is able of distributing these data to several voice conference participants.